Process and furnace for separating volatile from non-volatile material



Jan. 17, I967 A. LANGE ETAL 3,298,825

' PROCESS ANDv FURNACE FOR SEPARATING VOLATILE FROM NON-VOLATILEMATERIAL Original Filed June 6, 1958 INVENTORS ALFPED L/hv' k/OAK/V/M3407x422 United States Patent Ofiice 3,298,825 Patented Jan. 17, 19673,28,825 PROCESS AND FURNACE FOR SEPARATING VOLATILE FROM NON -VOLAT1LEMA- TERIAL Alfred Lauge and Joachim Barthel, Freiberg, Germany,assignors to Veb Mansfeld-Kombiuat Wilhelm Pieck, Eisleben, GermanyContinuation of application Ser. No. 740,419, June 6, 1958. Thisapplication July 15, 1963, Ser. No. 295,115 Claims. (Cl. 75-63) Thisapplication is a continuation of application Serial No. 740,419, filedJune 6, 1958 and now abandoned.

This invention relates to a process and to apparatus for separatingvolatile metals, metal compounds and the like at high temperature from araw material containing said metals or compounds while the raw materialis suspended in a gaseous phase.

Volatilization of metals and their compounds at a practical ratefrequently requires high temperatures which cannot always be reached forreasons of economy. It is, however, possible to operate at relativelylow temperatures if a gas is made to pass at high relative velocity overthe surface of the volatile material or if a highly volatile compound isformed by reaction of a relatively non-volatile metal or compound withthe gas or a compound suspended therein.

It has been proposed to blow a stream of pulverized raw materialtogether-with a stream of gas into a reaction vessel where the volatilecomponents are removed and carried off by the flowing gas. In order tomaintain the necessary relative velocity of gas and suspended solid, andto keep the solid particles in suspension, a high degree of turbulenceboth in the direction of flow and at right angles to it is required. Thearrangement above described, however, either leads to rapidsedimentation and premature removal of the solid particles from thestream of gas, or to entrainment of the solid by the gas whereby therelative velocity of gas and solid drops below the effective minimumvalue and the solid is carried out of the high temperature zone of thereaction vessel before the reaction of volatilization can be advanced toa satisfactory degree.

It is an object of the present invention to provide a method forvirtually complete separation of volatile components from a raw materialcomprising volatile metals, metal compounds, and the like.

It is another object of the invention to provide effective control meanspermitting to adjust the process conditions over a practical range.

It is still another object of the invention to provide apparatus forperforming the aforementioned process.

Other objects and features of this invention will become apparenttothose versed in the art as the disclosure is made in the followingdetailed description of a preferred embodiment of the invention asillustrated in the accompanying drawing in which:

The only figure is a vertical sectional view of a preferred embodimentof the apparatus of the invention.

A reverberat-ory furnace generally shown at 1 and equipped with a hearth2 which rises towards the flue 3 is provided with a vertical hollowshaft 4 located above the hearth 2. At the top of shaft 4 there is anopening 5 for admitting the charge into the upper portion 14 of shaft 4which serves as a primary reaction chamber. Nozzles 15 and 16 permitfuel and air to be injected into the reaction chamber. An additionalnozzle 17 located near the lower end of shaft 4 permits injection ofmaterial into the stream of exhaust gases from reaction chamber 14.

Briefly, the invention pertains to a process and apparatus forseparation by volatilization of metals, metal compounds, and the likefrom their ores, concentrates and other intermediate products ofextractive metallurgy, and other solid mixtures or compounds. Thevolatilized materials are carried out of the reaction or volatilizationzone and driven off by the exhaust gases from which they are separatedby well known methods, whereas slag and other non-volatile components ofthe raw material are collected in a receptacle outside the primaryreaction zone and are withdrawn in the molten or solid state.

Referring to the drawing which illustrates a preferred embodiment ofapparatus for performing the process of the invention, the charge of rawmaterial which may contain or may be pre-mixed with the fuel andslag-forming additions is admitted through the opening 5 at the top ofthe shaft whereby the solid material is carried into the primaryreaction chamber 14 by gravity in a vertical direction or flow. Fuel andair of combusion are injected into the reaction chamber 14 throughnozzles 15 and 16 respectively. A zone of high temperature forms inchamber 14 by their combustion, the temperature being above thetemperature of volatilization required. We prefer to arrange paired fueland air nozzles on opposite Walls and to inject air and fuel at highvelocity thereby creating high turbulence in the reaction chamber. Theinjected streams of fuel and air are admitted in a directionsubstantially transverse to the direction of flow of the particles ofraw material. If the streams of fuel and air enter in a radialtransverse direction, turbulence is predominantly horizontal, whereasthe contents of thereaction chamber 14 can be made to spin about theaxis of shaft 4 by tangential transverse injection of fuel and air. Theturbulence created by the design of the invention causes the charge toremain in suspension for a period sufficient to complete reaction orvolatilization within the reaction chamber.

While the shaft and its chamber portion have been described above asbeing heated by the combustion of the injected fuel in the furnaceillustrated, it is apparent that other sources of high temperature maybe utilized or that the heat of reaction of the charge with air or othergases, capable of reacting with the volatile components thereof, may besufficient to maintain the desired temperature. The height, diameter,and shape of the shaft may also be modified substantially to suit theprop erties of a specific raw material. Where the high temperature ofthe reaction chamber is achieved by means other than combustion withair, suitable inert gases are introduced through nozzles 15 and 16 tocreate turbulence.

The rate of reaction, the flow rate of the reaction gases, and theircomposition can be controlled by varying the degree of comminution ofthe charge, and the amount, proportions and composition of the fuel andcombustion air.

Furthermore, an inert gas, a gas capable of reacting with the volatilecomponents, secondary combustion air, or a mixture of these gases may beintroduced into a secondary reaction zone near the lower part of theshaft through nozzle 17.

While a gaseous or liquid fuel containing a relatively high percentageof hydrogen or hydrocarbon is usually preferred, other gaseous, liquidor solid fuels may be injected through nozzles 15 and 16 in order toachieve a specific reaction atmosphere. The combustion equilibrium andthereby the rate of reaction may further be influenced by introducingsteam, carbon dioxide or both into reaction chamber 14 or into the pathof the exhaust gases outside the reaction chamber through nozzles suchas 17 located in the shaft or near the hearth. The rate of gas flow inany part of the furnace may be increased by introducing inert gaseswhich may act as diluents when fed to the reaction zone. Secondary airof combustion and other reactive gases may be injected through nozzle17. We further contemplate operation with an excess of air over thatrequired for combustion of the fuel whereby oxidation of volatilecompounds or formation of volatile oxidation products from non-volatilematerial may be achieved. Such modifications and others not specificallyenumerated will readily present themselves to those skilled inextractive metallurgy and in other chemical and related arts to whichour process and apparatus may be applied.

The hearth 2 rises towards the flue 3 so that entrained liquid dropletsof non-volatile material may be deposited and drain back into thehearth. We prefer to equip the furnace with mechanical means forcollecting fiy-dust such as a dust chamber in the flue.

We have found that volatile compounds such as zinc sulfide can bepractically completely removed from ores and similar materials attemperatures between 1,000 and 1,600 C. The process of the invention isparticularly applicable to ores containing organic combustible materialsuch as for example bitumen, oil or carbon.

We have also found that concentrates of sulfidic ores such as fermginouszinc blende can be processed by our method under oxidizing conditions sothat the volatile sulfides, especially those of zinc and lead arevolatilized and oxidized and can be recovered from the flue gases,whereas the non-volatile sulfides such as those of copper and irontogether with the noble metals collect in a matte which can be withdrawnfrom the hearth together with the slag. It is apparent that the processcan be modified to yield metal from the matte by the roast-reductionprocess.

The results achieved by the method of the invention in equipment of thetype shown in the drawing are illustrated by two representativeexamples.

Example 1 A charge of 1100 lbs. of a lean ore containing 2.9% zinc and0.6% lead was comminuted to an average grain size of 0.3-0.4 mm. and wasprocessed at a temperature of 1,200 C. The slag which collected in thehearth weighed 787 lbs. and contained 0.82% zinc and 0.06% lead,indicating that 80% of the zinc and 93% of the lead present in thecharge had been volatilized. The fiy-dust recovered contained 43.8%zinc, 17.7% lead and 3.0% silica.

Example 2 3,640 lbs. of a :1 mixture of zinc blende concentrate and leanore having an average composition of 41.8% zinc and 0.96% lead werepulverized and processed at 1,200 C.

904 lbs. of slag containing 6.77% zinc and 0.06% lead were obtained. 96%of the zinc originally present and 99% of the lead had been volatilized.The fly-dust contained 60.8% zinc, 2.7% lead, 10% silica, and 1.8% iron.The matte contained 56.6% copper, 5.9% zinc, 0.1% lead and 6.4% iron.

While we have described our method and special apparatus for itsperformance in their application to the recovery of volatile sulfidesfrom a. mixed sulfidic raw material, it is understood that thisdisclosure is for the purpose of illustration, that the method andapparatus are equally applicable to the separation of non-volatileadmixtures from volatile metal compounds not of a sulfidic nature, andgenerally from materials which are either volatile at elevatedtemperatures or can be transformed into volatile compounds by reactionwith gases introduced into the reaction zone.

What we claim is:

1, A process for separating volatile and non-volatile components fromraw material containing metal values comprising the steps of initiallyadmitting said raw material in a finely divided form in .a downwarddirection directly into the primary reaction zone of a furnace having ahearth situated beneath said reaction zone and extending rearwardlytherefrom into communication with a flue which is situated to the rearof said hearth and extends upwardly therefrom, maintaining said reactionzone above the temperature of volatilization of said volatilecomponents, suspending said raw material by injecting a stream of gasradially into said reaction zone in a direction substantially transverseto the direction of flow of said raw material at a velocity sufficientto create a turbulence in said reaction zone, maintaining said materialin suspension until the volatile components thereof are substantiallydriven off by exhaust gases from said zone containing said gaseousvolatile components, and exhausting them first in a downward directionfrom said reaction zone, then rearwardly over said hearth, so thatentrained liquid droplets of non-volatile material will be deposited onsaid hearth, and finally out through said flue.

2. A process for separating volatile and non-volatile componentsaccording to claim -1, including the step of mixing the raw materialwith fuel prior to admitting said raw material into said primaryreaction zone.

3. A process according to claim 1, including the step of introducing asecondary supply of gas into the downward flow of said volatilecomponents and exhaust gases outside of said primary reaction zone.

4. A process as recited in claim 1 and wherein said raw materialincludes zinc and lead in comminuted form, and said gaseous volatilecomponents including volatilized zinc and lead.

5. A process as recited 'in claim 1 and wherein said raw materialincludes a mixture of zinc blende concentrate and an ore which ispulverized and includes zinc and lead, said gaseous volatile componentsincluding volatilized zinc and lead.

References Cited by the Examiner UNITED STATES PATENTS Re. 12,424 12/1905 Brown 26 156,243 10/ 1874 Wheeler 7526 1,936,092 11/1933 Kuzell7586 1,949,905 3/1934 Hall 7586 1,961,424 6/1934 .Maier 7586 2,128,3798/1938 Spencer 75--1 2,184,300 12/1939 Hodson et al. 7526 2,194,454 3/1940 Greenawalt 7574 2,456,918 12/ 1948 Church 7567 2,478,912 8/1949Garbo 7526 2,613,074 10/1952 Woods 26615 2,636,817 4/ 1953 Knechtel 75862,682,462 6/ 1954 Woods 7586 2,951,756 9/1960 Cavanagh 7540 3,065,95811/1962 Cerych et a1. 266-15 FOREIGN PATENTS 921,861 1/1947 France.

HYLAND BIZOT, Primary Examiner.

DAVID L, RECK, Examiner.

H. W. CUMMINGS, H. W. TARRING,

Assistant Examiners.

1. A PROCESS FOR SEPARATING VOLATILE AND NON-VOLATILE COMPONENTS FROMRAW MATERIAL CONTAINING METAL VALUES COMPRISING THE STEPS OF INITIALLYADMITTING SAID RAW MATERIAL IN A FINELY DIVIDED FORM IN A DOWNWARDDIRECTION DIRECTLY INTO THE PRIMARY REACTION ZONE OF A FURNACE HAVING AHEARTH SITUATED BENEATH SAID REACTION ZONE AND EXTENDING REARWARDLYTHEREFROM INTO COMMUNICATION WITH A FLUE WHICH IS SITUATED TO THE REAROF SAID HEARTH AND EXTENDS UPWARDLY THEREFROM, MAINTAINING SAID REACTIONZONE ABOVE THE TEMPERATURE OF VOLATILIZATION OF SAID VOLATILECOMPONENTS, SUSPENDIND SAID RAW MATERIAL BY INJECTING A STREAM OF GASRADIALLY INTO SAID REACTION ZONE IN A DIRECTION SUBSTANTIALLY TRANSVERSETO THE DIRECTION OF FLOW OF SAID RAW MATERIAL AT A VELOCITY SUFFICIENTTO CREATE A TURBULENCE IN SAID REACTION ZONE, MAINTAINING SAID MATERIALIN SUSPENSION UNTIL THE OLATILE COMPONENTS THEREOF ARE SUBSTANTIALLYDRIVEN OF BY EXHAUST GASES FROM SAID ZONE CONTAINING SAID GASEOUSVOLATILE COMPONENTS, AND EXHAUSTING THEM FIRST IN A DOWNWARD DIRECTIONFROM SAID REACTION ZONE, THEN REARWARDLY OVER SAID HEARTH, SO THATENTRAINED LIQUID DROPLETS OF NON-VOLATILE MATERIAL WILL BE DEPOSITED ONSAID HEARTH, AND FINALLY OUT THROUGH SAID FLUE.